Recently, downsizing or light weightening is strongly required for batteries to be used for a power source of electrical devices or vehicles or the like. With respect to an package of the battery, packages using a laminated film have increased, instead of conventional type that uses a metal case. As a laminated film, in general, aluminum is used for a metal foil; nylon (registered trademark) or polyethylene terephthalate is used for a heat-seal resin film on the outer surface of the battery, and polyethylene or polypropylene is used for the inner surface. A film packaged battery is a battery in which the battery element is accommodated in the package made of the laminated film (also referred to as “packaging film”) together with electrolyte. Positive electrode tab and negative electrode tab come from the battery element, and each of the electrode tabs extends toward outside of the packaging film.
However, when an impact force is applied to the film packaged battery, the battery element might move within the packaging film. This would cause troubles such as a disconnection between the battery element and the electrode tab or a short between the positive electrode and the negative tab or between the negative electrode and the positive tab. To secure the packaging film and the battery element, a connecting technique is known in which the positive current collector and the negative current collector are connected to a heat-seal layer inside of the laminated film by heat-sealing, for example (Patent Document 1). Additionally, a separator that covers the outermost surface of the battery element is connected to the heat-seal layer inside of the laminated film by heat-sealing (Patent Document 2). It is also known that the battery element and a battery case are secured by using a seal tape that includes the thermosetting resin adhesive material (Patent Document 3).